NEW YORK (Reuters Health) - Replacing hepatitis B vaccine with a vaccine active against hepatitis A and B at U.S. sexually transmitted disease clinics would provide the additional protection in a cost-effective manner, investigators report. A hepatitis A/B vaccine is available and is administered on the same schedule as hepatitis B vaccine.

R. Jake Jacobs and Allen S. Meyerhoff, from Capitol Outcomes Research, Inc., based in Alexandria, Virginia, note in their report in the November issue of Sexually Transmitted Diseases that hepatitis A vaccination is cost-effective for children and adolescents. However, previous analyses have concluded that the same is not true for older adults when including individuals age 50 years and older. .

The two researchers used a Markov model of hepatitis A outcomes to estimate the cost-effectiveness of using the dual vaccine. They considered a hypothetical cohort of 1 million adults ages 18 to 30 years old seen at public STD clinics during 2002. They conservatively assumed the same age-specific risks as other Americans.

The model estimates that 10,381 infections, 1480 hospitalizations and 48.4 deaths due to hepatitis A would occur during the next 5 decades in the absence of hepatitis A immunization. They assumed an additional cost of hepatitis A/B vaccination over hepatitis B vaccination alone of $36 for all three doses in a public setting. However, they note, the cost would be more than three times higher if purchased in the private sector.

Vaccinating would prevent 2263 cases, reducing treatment costs by $2.5 million. Vaccine costs would be $20,891 per life-year saved and $13,397 per QALY saved. All sensitivity analyses resulted in costs of no more than $42,000 per life year or $25,000 per QALY.

Because of their conservative estimates, they point out, bivalent immunization may be even more cost-effective than their analyses showed.

The authors note that the Advisory Committee on Immunization Practices recommends adult immunization for those at increase risk, including IV drug users, travelers to high-prevalence destinations, and men who have sex with men. However, many patients do not report their risk factors, making it difficult to identify the optimal target population.

The analysis is relevant only to a population of young adults attending STD clinics, Meyerhoff told Reuters Health. "The compliance in this population is lower than one would expect in the general population," he explained. His group assumed that only 34% would accept the first dose, and that among these, 38% would come back for the second dose and 16% for the third.

Another reason that the bivalent vaccine may not be cost-effective for those treated in the private sector, he added, is that they cannot obtain vaccines as cheaply as can public health clinics. Furthermore, their assumption is that STD clinic attendees would be more susceptible to hepatitis A because of their immune status.